1 Introduction

The GNU Autoconf Archive is a collection of more than 500 macros for
GNU Autoconf that have
been contributed as free software by friendly supporters of the cause from
all over the Internet. Every single one of those macros can be re-used
without imposing any restrictions whatsoever on the licensing of the
generated configure script. In particular, it is possible to
use all those macros in configure scripts that are meant for
non-free software. This policy is unusual for a Free Software Foundation
project. The FSF firmly believes that software ought to be free, and
software licenses like the GPL are specifically designed to ensure that
derivative work based on free software must be free as well. In case of
Autoconf, however, an exception has been made, because Autoconf is at such a
pivotal position in the software development tool chain that the benefits
from having this tool available as widely as possible outweigh the
disadvantage that some authors may choose to use it, too, for proprietary
software.